This project is a study of bacterial Shiga toxin action on human endothelial cell function/physiology underlying the vascular pathology seen in hemolytic uremic syndrome (HUS) and hemorrhagic colitis (HC). In humans, these conditions are associated with Shiga toxin-producing bacterial dysentery pathogens, Shigella dysenteriae 1 and selected Escherichia coli serotypes. Our continuing investigations have focused on direct interaction of Shiga toxins with the vascular endothelium, in vitro. It is proposed that Shiga toxins are responsible for the development of vascular damage an coagulation observed in the kidney glomeruli of HUS patients. The goals of this project are to further describe, at the endothelial cell level, how the Shiga toxins cause life-threatening vascular disease. Our long-term objective is to utilize information obtained from this project to develop rational therapeutic intervention for these and perhaps other related vascular diseases. An emphasis has been placed on the use of human kidney cell lines in the following studies. The research plan includes a series of in vitro coagulation tests and hemostatic assays. In addition, there will be an analytical assessment of procoagulation and anticoagulation factors produced by human vascular endothelial cells following exposure of these cells to Shiga toxin. Adherence of platelets and neutrophils to these cells is also to be examined in regard to the procoagulation state induce by Shiga toxin. Further, the role of extracellular cell matrix is to be studied following toxin-damage of endothelial cells. The combined effects of potent endotoxin-induced cytokines (eg. IL-1 and TNF) and Shiga toxin on vascular endothelium will also be examined in relation to the development of the vascular disease states of HUS and HC. Finally, a new facet of Shiga toxin action to be explored is the role of human kidney juxtaglomerular cells in development of HUS. Together, data derived from this research should add to our knowledge of Shiga toxin action and of vascular HUS/HC disease.